The present inventions relate to medical probes, and more particularly, catheters and surgical probes that possess temperature sensing functionality.
Currently, medical probes, such as catheters and surgical probes, are used to treat heart abnormalities, such as atrial fibrillation and other cardiac arrythmias. In a typical procedure, a medical probe employs one or more ablation elements and one or more corresponding temperature sensors in order to therapeutically ablate tissue within the heart in a controlled manner. Temperature sensors currently used in medical probes, such as thermistors or thermocouples, all require separate analog signal conditioning circuitry for each sensor, although analog to digital (A/D) conversion circuitry may be multiplexed.
Thermistors respond to changes in temperature with a well-defined change in resistance. Analog conditioning circuitry, which is used to interface the thermistors with the A/D converter, measures the resistance of the thermistors, and thus, the temperature of the adjacent tissue, by separately measuring the voltage across each thermistor in response to a constant current. By comparison, thermocouples contain a junction of dissimilar metals that generate a small voltage proportional to temperature, due to the Peltier effect. Analog conditioning circuitry is connected to each thermocouple to amplify the voltage output thereby and to reduce any noise associated with such voltage.
Further, to support such multiple sensor probes, current technology requires a large number of wires to be contained within the small and limited space of the probe body, thereby rendering manufacture of such medical probes increasingly difficult. This constraint is even more pronounced in catheters, the diameters of which must be minimized to allow the catheters to be introduced into the heart through the vasculature of a patient. The increased number of wires in connectors and cabling also makes the manufacture of accessory cables used to support multiple sensor medical probes more difficult and expensive. Moreover, connector reliability is reduced due to the large number of connections required to implement discrete wires for each temperature sensor.
Regardless of the type of sensor utilized, the analog conditioning circuitry must be duplicated with the currently available designs for each sensor. For example, FIG. 29 illustrates a prior art system, which includes a power generator 66 that is coupled to a medical probe 50 via a cable 55. A standard generator interface 62 is used to interface the proximal end of the cable 55 to the circuitry within the generator 66, and a standard probe interface 62 is used to interface the distal end of the cable 55 to the circuitry within the medical probe 50. The power generator 66 includes a power source 51 (in this case an RF oscillator), which provides RF power to ablation energy electrodes 53 located at the distal end of the medical probe 50. The power generator 66 further includes a temperature controller 54 (in this case, a microprocessor), which communicates with analog temperature sensors 52 located at the distal end of the medical probe 50 via parallel sets of analog to digital converters 56 and signal conditioners 60. As illustrated, a separate analog to digital converter 56 and signal conditioners 60 is required for each temperature sensor 52.
FIG. 30 illustrates another prior art system, which includes a power generator 68 that is coupled to the medical probe 50 via the cable 55. The power generator 68 differs from the power generator 66 shown in FIG. 29 in that the power generator 66 uses a single analog to digital converter with multiplexing capability 58 to process signals from each sensor 52.
The additional circuitry required for each sensor 52 generally involves expensive, low noise integrated circuits. Time consuming calibration of each input during manufacturing is also typically required. As a result, the amount of circuit duplication increases by the number of sensors that must be read, thereby making systems with more than a few temperature sensors expensive and impractical. Also, the ablation power generators that support these medical probes are necessarily designed in a non-optimal manner. For a multiple sensor medical probe, the ablation power generators must be designed to accommodate the number of expected sensors by providing separate analog inputs for each sensor, as illustrated in FIGS. 29 and 30. Therefore, when designing such power generators, a tradeoff must be made between the excessive costs of providing extra sensor inputs to accommodate future requirements and the risk of premature obsolescence of a power generator that provides too few sensor inputs.
Moreover, the sensors are typically located from between ten to fifty feet away from the ablation power generators, being connected through fine-gauge wire in the medical probe itself, and through one or more cables with intermediate connections. The analog voltages which represent the temperature are typically quite small, particularly with thermocouples, where the dynamic range in the area of interest is usually only in the hundreds of microvolts. These analog voltages are susceptible to electrical noise induced by ablation power and sources of electromagnetic interference in the environment, some of which may be of a high enough amplitude or low enough frequency range that filtering may not be practical.
Consequently, there is a need to provide a medical probe system that contains a reduced number of electrical paths, or temperature sensor wires, as well as a medical probe system that outputs temperature sensor signals that exhibit little or no noise.
The present inventions are directed to medical probe systems, medical probes, ablation power generators, and temperature sensor subassemblies that are configured to reduce the number of wires used to conduct data output from a multitude of temperature sensors. The present inventions are also directed to medical probes that utilize one or more digital temperature sensors, resulting in a temperature sensing circuit that is less susceptible to ambient noise.
In accordance with a first aspect of the present inventions, a medical probe comprises an elongate member having a proximal end and a distal end. The medical probe can be any probe (e.g., a catheter or surgical probe) that can be placed within the body of a patient. The medical probe further includes a plurality of temperature sensors that are carried by the distal end of the elongate member. Each of the temperature sensors can be digital, in which case, it may conveniently be embodied in an integrated circuit that is configured for outputting digital data representative of a measured temperature. Alternatively, each of the temperature sensors can be analog, in which case, it may be embodied in a thermistor, thermocouple, resistance temperature detector (RTD), or other analog device, that is configured for outputting analog data representative of a measured temperature.
The medical probe further includes a common electrical bus carried by the elongate member. The common electrical bus defines two or more electrical paths, each of which is coupled to the plurality of temperature sensors. By way of nonlimiting example, the two or more electrical paths can comprise three electrical paths represented by respective data, ground, and power lines. Alternatively, power can be parasitically obtained from the data line, in which case, only two electrical paths are needed. The common electrical bus can be embodied in any suitable circuit, e.g., bifilar wire, trifilar wire, flex circuit, or flex circuit/wire hybrid. Each electrical path can be formed of a single wire or trace to which the temperature sensors are connected, or alternatively, can be formed of several wires or traces connected between the temperature sensors in a daisy chaining fashion. In the preferred embodiment, the medical probe includes a handle mounted to the proximal end of the elongate member. The handle includes an interface for connecting the two or more electrical paths to a cable that provides a connection between the medical probe and a console, such as an ablation power generator.
By using a common electrical bus, temperature sensor data from all of the temperature sensors can be conducted within the medical probe using a minimal number of electrical paths. The common electrical bus may extend through the elongate member, directly connecting to the temperature sensors, in which case, the number of electrical paths extending through the medical probe, as well as the connecting cable, can be reduced. Alternatively, the common electrical bus may be located at the proximal end of the medical probe, and indirectly coupled to the temperature sensors through a second electrical bus, in which case, the number of electrical paths extending through the connecting cable can be reduced.
In the preferred embodiment, the medical probe is an ablation probe that includes one or more electrodes carried by the distal end of the elongate member. In this case, the temperature sensors may be located adjacent the electrodes to provide temperature measurements of the tissue during the ablation process. By way of nonlimiting example, the one or more electrodes can be embodied in a segmented electrode, an electrically conductive balloon electrode, a microporous balloon electrode, or a balloon activated splined electrode assembly. If segmented, the electrodes can be, e.g., rigid conductive ring electrodes, spiral coil electrodes, ribbon electrodes, and printed-on electrodes. The one or more electrodes can also comprise a tip electrode. In an ablation probe, the temperature sensors are preferably disposed between the corresponding electrodes and elongate member in contact with the electrodes. Alternatively, the profile of the medical probe can be further reduced by mounting the temperature sensors in beveled openings formed within the corresponding electrodes and arranged therewith in a flush manner.
In accordance with a second aspect of the present inventions, a temperature sensor subassembly comprises a plurality of temperature sensors, and a common electrical bus having two or more wires, each of which is coupled to the plurality of temperature sensors. In the preferred embodiment, the two or more wires are laser stripped to expose attachment points for the plurality of temperature sensors. The temperature sensor subassembly can be embodied in any suitable circuit, e.g., bifilar wire, trifilar wire, flex circuit, or flex circuit/wire hybrid. Each of the temperature sensors can be digital, in which case, it may conveniently be embodied in an integrated circuit that is configured for outputting digital data representative of a measured temperature. Alternatively, each of the temperature sensors can be analog and associated with multiplexing circuitry, in which case, it may be embodied in a thermistor, thermocouple, resistance temperature detector (RTD), or other analog device, that is configured for outputting analog data representative of a measured temperature. The temperature sensor subassembly can be utilized in any assembly or system that requires a multitude of adjacent temperature sensors. Such assembly may include, but is not limited to, medical probes.
In accordance with a third aspect of the present inventions, a medical probe comprises an elongate member, and one or more temperature sensor subassemblies carried by the elongate member. Each of the one or more temperature sensor subassemblies comprises a plurality of temperature sensors and a common electrical bus connected to the plurality of temperature sensors. The temperature sensor subassemblies can be variously configured on the elongate member. By way of nonlimiting example, a single temperature sensor subassembly can extend along one side of the elongate member. In another embodiment, two temperature sensor subassemblies can extend along opposite sides of the elongate member. In still another embodiment, a single temperature assembly can extend along the elongate member in a spiral fashion. In yet another embodiment, a temperature assembly can be in the form of a ring temperature assembly circumferentially extending around the elongate member. To minimize the profile of the medical probe, the one or more temperature sensor subassemblies can be situated in one or more skives formed on the elongate member. In the preferred embodiment, the medical probe is an ablation medical probe that comprises one or more electrodes, in which case, the temperature sensors are located adjacent the one or more electrodes.
In the preferred embodiment, the elongate member comprises an elongate tube with an internal lumen, in which case, each data bus can extend into the internal lumen through orifices made through the elongate tube. Such orifices can be used to simply route each data bus from the exterior of the tube, through the internal lumen back to the proximal end of the medical probe. These orifices can also be used to connect temperature sensors on opposite sides of the elongate member. For example, alternating temperature sensors of one of the temperature sensor subassemblies can be mounted on opposite sides of the tube, with the data bus traversing the internal lumen through orifices formed in the tube on opposite sides thereof. The orifices can also be used to provide slack in each data bus, thereby allowing the medical probe to flex without causing damage to the temperature sensor subassemblies. For example, the plurality of temperature sensors can be mounted on an exterior surface of the tube, and the data bus can be looped inside of the internal lumen through pairs of orifices formed through the tube between the temperature sensors.
In accordance with a fourth aspect of the present inventions, a medical probe comprises an elongate member having a distal end carrying a plurality of digital temperature sensors. Each of the digital temperature sensors is configured to output a digital signal representative of a measured temperature. In this manner, the temperature sensor capability of the medical probe is less susceptible to ambient noise. The digital temperature sensors can be conveniently embodied in integrated circuits. The medical probe further includes a common electrical bus extending through the elongate member, and defining two or more electrical paths, each of which is coupled to the plurality of digital temperature sensors. The two or more electrical paths may define a data line and a ground line. The data line can optionally be used by the digital temperature sensors in a parasitic manner as a power line. In the preferred embodiment, each of the plurality of digital temperature sensors exhibits a unique digital address, thereby allowing temperature data to be individually obtained from each individual digital temperature sensor over the common electrical bus. In the preferred embodiment, the medical probe is an ablation medical probe comprising one or more electrodes, in which case, the plurality of digital temperature sensors are located adjacent the one or more electrodes to facilitate the tissue ablation process.
In accordance with a fifth aspect of the present inventions, a medical probe comprises an elongate member having a distal end carrying a digital temperature sensor. The digital temperature sensor can be conveniently embodied in an integrated circuit. The medical probe further includes an electrical bus extending through the elongate member, and coupled to the digital temperature sensor. In the preferred embodiment, the electrical bus comprises a data line and a ground line. The digital temperature sensor can advantageously use the data line as a power line in a parasitic manner. The medical probe may be an ablation medical probe comprising an electrode, in which case, the digital temperature sensor is located adjacent the electrode.
In accordance with a sixth aspect of the present inventions, a temperature sensing ablation system comprises a medical probe,,a cable, and an ablation power generator. The type of ablation power generator that may be implemented with the system include, e.g., a RF ablation power generator, a microwave ablation power generator, an ultrasound ablation power generator, and a cryoablation power generator. The medical probe comprises an elongate member having a proximal end and a distal end. The medical probe further comprises at least one electrode and a plurality of temperature sensors (e.g., digital sensor chips), which are carried by the distal end of the elongate member. The medical probe further comprises ablation leads that extend through the elongate member and are coupled to the at least one electrode. The medical probe further includes a common electrical bus carried by the elongate member. The common electrical bus defines two or more electrical paths, each of which is coupled to the plurality of temperature sensors. The common electrical bus can extend through the elongate member and be connected directly to the temperature sensors, or alternatively, be located within the proximal end of the elongate member, in which case, an intermediate electrical bus can connect the common electrical bus indirectly to the temperature sensors.
The ablation power generator is coupled to the medical probe through the cable. In this respect, the ablation power generator is configured for receiving temperature data from the plurality of temperature sensors, and being configured for controllably transmitting energy to the at least one electrode based on the received temperature data. In the preferred embodiment, the medical probe comprises a handle carried by the proximal end of the elongate member. The handle carries an interface to connect the cable to the ablation leads and common electrical bus.
In accordance with a seventh aspect of the present inventions, an ablation power generator for delivering ablation power to a medical probe is provided. The ablation power generator comprises a power source and temperature control circuitry. The power source is capable of delivering ablation power to ablation elements located on the medical probe, and can take the form of, e.g., an RF power source, cryoablation power source, or ultrasound power source. The temperature control circuitry is designed to communicate with digital temperature sensors located on the probe, and may comprise, e.g., a microprocessor.
The power generator preferably includes an interface that allows the generator to mate with a cable and subsequently to the probe. The interface enables the power generator, and specifically the temperature control circuitry of the power generator, to receive digital data from the interface. In one embodiment, the power generator is configured to communicate with a medical probe that has a plurality of digital temperature sensors. In this embodiment, the power generator includes an interface configured for serially receiving digital data from the plurality of digital sensors, in which case, the temperature control circuitry is designed to receive the digital data from the interface.
In accordance with an eighth aspect of the present inventions, an ablation power generator designed for use with a medical probe having at least one ablation element and a plurality of temperature sensors located on a common data bus is provided. The temperature sensors may be either digital or analog sensors. The power generator is configured to deliver ablation power to the ablation element. The power generator further includes temperature control circuitry that communicates with the temperature sensors located on the common data bus.
These and other aspects of the present invention are described herein in greater detail.